Page -> Preview Page as User

[aembler]

Currently, if you enable advanced permissions in 5.7.0-wip you'll get "Preview Page as User" in the lefthand page panel. This panel currently doesn't do anything. We need to do the following.

Create a route for a new sub-panel in config/routes.php, routing to a new controller: $rl->register('/system/panels/page/preview_as_user', 'PagePreviewAsUserPanelController::view');

Create a new controller panel for this.

Add a view for this panel at views/panels/page/preview_as_user.php that our controller is set up to use.

Make this panel actually contain the fields from the old preview as user dialog box.

Make this panel look like the other panels using the .ccm-panel-dark() mixin. Add CSS information to ccm_app/panels.less and ccm_app/panels/preview_as_user.less where necessary.

The timed permission list also still has to continue to work on this page.

Reference the existing preview panel detail view and modify it to accept optional date and time parameters.

Make sure the new request library is set up to honor passed-in datetimes as well as users.